Abstract
Objective:
The impact of pressure glove tightness on maximum grip force, muscle activity, and psychophysical responses is investigated to facilitate the prescription of a suitable reduction factor (RF) for pressure treatment.
Background:
The wearing of pressure therapy gloves is often considered to hinder hand performance and cause discomfort, resulting in unsatisfactory treatment adherence during burn rehabilitation.
Method:
A wear trial was carried out with 10 participants for three custom-made pressure gloves that consist of different RFs—10%, 15% and 20%—as well as for the bare hand. The surface electromyography of three forearm muscles was measured during tasks that involve moving marbles, buttoning a shirt, and typing. The psychophysical responses were also recorded.
Results:
The use of pressure gloves results in a reduction in the maximum gripping force. Gloves with tighter pressure contribute to lower perceived comfort and ease of hand motion. Increased glove tightness (with RFs of 15% and 20%) decreases muscle activity as compared to the bare-hand condition when buttoning a shirt. In terms of typing, the forearm muscle activity increases with high glove pressure (RF of 20%).
Conclusion:
The forearm muscles are significantly affected by glove tightness in performing different daily tasks that required gripping, pinching, and typing. The increase of RF of pressure gloves causes negative impact on psychophysical response and handgrip strength. Glove tightness in relation to hand performance and comfort is important in prescribing an optimal pressure therapy glove for hypertrophic scar treatment.
Application:
The findings give insight into the impacts of pressure glove tightness on muscle activity, thus providing a reference for glove development.
Introduction
Pressure therapy garments have been the mainstay of hypertrophic scar treatment since the 1970s (Bombaro et al., 2003; Bousfield, 2002; Macintyre & Baird, 2006; Macintyre, Gilmartin, & Rae, 2007; Macintyre, Mitchell, Baird, & Weedall, 1999; Ward, 1991). They are noninvasive and especially important for treating hypertrophic scars that may have negative impacts on hand functions and/or result in a clawed hand. Previous studies on the use of pressure therapy garments have mainly focused on the evaluation and determination of an ideal interfacial pressure that could control the formation of excess wound collagen (Costa et al., 1999; Giele, Liddiard, Currie, & Wood, 1997; Larson, Abston, Evans, Dobrkovsky, & Linares, 1971; Macintyre, Baird, & Weedall, 2004).
Researchers have indicated that continuous pressure at a capillary level of 25 mmHg could affect the realignment of collagen bundles and might control overexuberant collagen synthesis (Bousfield, 2002; Cheng et al., 1984; Ward, 1991). In order to achieve the desired pressure delivery, the pressure garments are made with a 10% to 20% reduction factor, which indicates the amount of reduction in circumferential dimensions of the actual body parts. The magnitude of pressure delivered by the garment is the first consideration in the fabrication process. However, the impacts of pressure garments on human body responses primarily contributing to treatment adherence and hence treatment outcome are often neglected. Hence, to prescribe pressure therapy gloves that could provide the optimal amount of pressure and tightness for the treatment of hypertrophic scars, the subjective perceptions of applied pressure and the associated response of the wearer should also be taken into consideration.
Adherence to pressure garment therapy requires a strong commitment from patients in terms of cooperation. For optimum outcome of the treatment, the garments must fit like a second skin on patients and be continuously worn (24 hr a day) from the time that the wound has healed until the scar matures. As a scar requires half a year to several years to completely mature, patient compliance is an important aspect of pressure garment therapy. However, the rate of patient compliance of the continuous use of pressure garments has not been satisfactory (Johnson et al., 1994; Ripper, Renneberg, Landmann, Weigel, & Germann, 2009; Stewart, Bhagwanjee, Mbakaza, & Binase, 2000). The overall garment discomfort, as well as physical impairment and emotional stress caused by the garments, has been proven to be closely correlated to the rate of patient compliance during pressure garment therapy (Johnson et al., 1994; Macintyre & Baird, 2006) and thus the risk of formation of hypertrophic scars, cosmetic deformities of body parts, and even functional limitation. There are some patients who complain about the additional restriction of mobility caused by the pressure garments (Ward, Hayes-Lundy, Reddy, Brockway, & Mills, 1992). People use their hands in accomplishing different tasks in daily life. The feeling of discomfort and restriction in the mobility of hands caused by a pressure therapy glove can lead to inconvenience in carrying out tasks and daily activities, which may result in unsatisfactory treatment adherence.
As reported by numerous authors in the literature, work gloves, such as those made of leather, latex, vinyl, and nitrile, negatively influence grip and pinch strength, dexterity, ease of tool manipulation, and functional hand use (Bellingar & Slocum, 1993; Dianat, Haslegrave, & Stedmon, 2012b; Fleming, Jansen, & Hasson, 1997; Kinoshita, 1999; Riley, Cochran, & Schanbacher, 1985; Rock, Mikat, & Foster, 2001; Sawyer & Bennett, 2006; Shih, Vasarhelyi, Dubrowski, & Carnahan, 2001). O’Brien, Weinstock-Zlotnick, Hunter, and Yurt (2006) and Dewey et al. (2007) modified pressure gloves by using a suede, rubber, or silicon attachment on the palm surface, which can enhance hand function in gross- and fine-motor activities and functional grip as compared to traditional pressure gloves that are solely made of warp-knitted powernet fabrics. In addition, fit and thickness of work gloves have been found to affect the effort put forth by the wearers and the muscle activity and performance of their hands (Kovacs, Splittstoesser, Maronitis, & Marras, 2002; Wells, Hunt, Hurley, & Rosati, 2010). However, limited study is available to evaluate the influence of tightly fitted pressure therapy gloves on hand performance.
Surface electromyography (SEMG) measurement is a noninvasive biomechanical assessment that provides information on muscle activation characteristics (Yang & Winter, 1985). The SEMG amplitude is linearly related to the tension exerted by muscles and represents the force required of local muscles during a task (Milner Brown & Stein, 1975). Several studies have used SEMG to evaluate the effect of different work gloves or protective gloves on muscle effort (Claudon, 2006; Kovacs et al., 2002; Larivière et al., 2004, 2010; Wells et al., 2010; Willms, Wells, & Carnahan, 2009). Significant effects on the ratio of the peak force to flexor muscle SEMG activity between different glove types in term of material and fit have been reported. Thinner and better-fitting gloves were found to provide better transmission of muscular force to measured grip force (Kovacs et al., 2002). Increased glove thickness and stiffness were identified as the key attributes contributing to the increase of muscle effort to perform manual tasks (Larivière et al., 2010; Willms et al., 2009). However, there is a lack of research on the effect of pressure glove tightness on muscle activity. It is crucial to strike a balance between glove tightness and minimized influence on daily life. The use of SEMG to study muscle activity allows the effect of tightness from pressure gloves on the internal loading of muscles to be quantified. By evaluating the accompanying psychophysical responses, one can establish the impact of glove tightness on human biomechanical and psychophysical responses.
In this study, we investigate the effect of the tightness of pressure therapy gloves on the maximum grip force and forearm muscle effort in performing different tasks together with psychophysical responses. The quantitative results that are generated in this study will enable clinicians to understand the biomechanical effects of pressure therapy gloves on muscle activities generated during daily tasks and psychophysical comfort perception. The findings can also provide a reference for prescribing a suitable reduction factor of pressure gloves to improve the effectiveness of the treatment, with the ultimate goal of developing a glove that provides adequate pressure to treat hypertrophic scars with minimal amount of discomfort and higher rates of acceptance.
Method
Participants
Ten participants, five men and five women, were recruited from the university population. The age of the participants was 18 to 29 (M = 22.5, SD = 3.9), average height was 168.3 cm (SD = 8.8), and average weight was 59.66 kg (SD = 13.3). All were right hand dominant, were healthy, and had no musculoskeletal problems in the upper extremities and no history of hand or arm injury. Healthy participants were recruited in order to highlight the effect of glove tightness and avoid the interference of scars or hand disabilities. The anthropometric data measured on the right hand of the participants are presented in Table 1. The experiment was approved by the Human Subjects Ethics Sub-Committee at the Hong Kong Polytechnic University prior to beginning the study.
Hand Anthropometric Information of Participants
Apparatus and Materials
The independent variable was the tightness of the pressure glove. Four conditions were tested: three levels of glove tightness (with RFs of 10%, 15% and 20%) and the bare hand. The dependent variables were the normalized SEMG of three forearm muscles, grip strength, and psychophysical perception toward the glove-wearing comfort, ease of hand motion, and perceived exertion of hand during the wearing of glove.
Gloves
A 68/32 nylon/spandex powernet fabric, which is currently used by clinicians and manufacturers to make pressure therapy garments, was purchased for this study in the development of the glove prototypes. Three pressure gloves were tailor-made for each participant with applied RFs of 10%, 15% and 20%. In accordance with the pressure measuring method in our previous study (Yu, Yick, Ng, & Yip, 2013), the interfacial pressure given to the center of the hand dorsum while holding a cylindrical bottle (6.3 cm in diameter) was 23.95, 26.60, and 27.84 mmHg for gloves with RFs of 10%, 15%, and 20% respectively. All of the gloves had the same design with open fingertips reaching the distal interphalangeal (DIP) joint. The length of the thumb part reached the thumbnail; see Figure 1. The open fingertip design was adopted as it is typically used in clinical practice to improve tactile sensation (Dewey et al., 2007).
Pressure therapy gloves.
Surface electromyography
Disposable Ag/AgCl surface electrodes for measuring the SEMG were positioned on the belly of three muscles on the right forearm, including the flexor pollicis longus (FPL), extensor digitorum (ED), and flexor digitorum superficialis (FDS). The FPL muscle helps to control thumb interphalangeal (IP) flexion. The contraction of the FDS muscle leads to metacarpophalangeal (MP), proximal interphalangeal (PIP), and distal interphalangeal (DIP) flexion of fingers, and the contraction of the ED muscle results in extension and finger abduction of the MP, PIP, and DIP. These muscles are involved in tasks that require gripping, pinching, and typing and hence are representative of the demands required of the hands during the experimental activities and activities of daily living (Wells et al., 2010; Willms et al., 2009). Before application of the electrodes, the hairs on the overlying skin area were shaved and the skin was abraded to remove dead epidermal cells and then cleaned with alcohol. The raw SEMG signals of each muscle were collected at the rate of 2,048 samples per second, amplified (× 1,000), band-pass filtered (20–500 Hz), and 14 bits A/D converted through an SEMG system, the FlexComp Infiniti (Thought Technology Ltd., Canada). Maximum voluntary contraction (MVC) trials in accordance with the functional characteristics of the three muscles in the bare-hand condition were performed to obtain the maximum voluntary electrical activation (MVE) of the three muscles for normalization purposes. The MVC trials included maximum grip action, resisted thumb IP flexion, and isometric wrist extension and flexion (Mogk & Keir, 2003). Each trial was carried out four times. Each trial had a length of 8 s with at least 2 min of rest in between (Mathiassen, Winkel, & Hägg, 1995).
For SEMG signal processing, all the EMG signals were high-pass filtered at 20 Hz by using a fourth-order Butterworth IIR filter to remove artefacts and a 60 Hz notch filter to remove power line noise. Then the root mean square (RMS) amplitude of the SEMG signal (SEMGRMSµV) was computed with 50-ms sliding window (Basmajian & De Luca, 1985; Hagberg, 1979). The maximum 1,000-ms RMS value across all the MVC trials for each muscle was regarded as the MVE (MVERMSµV) and used as the reference value to normalize the signals (Hashemi Oskouei, Paulin, & Carman, 2013). The normalization was carried out according to the following equation: %MVE = (SEMGRMSµV/MVERMSµV) × 100 (Mathiassen et al., 1995). The amplitude probability distribution function (APDF) of the normalized signal was calculated for further analysis. The static level (P10), median level (P50), and peak level (P90) of APDF were obtained for analysis. Each percentile level describes the percentage of the recording time that the SEMG activity was at or below a certain %MVE level (Huysmans, Hoozemans, van der Beek, de Looze, & van Dieën, 2008; Jonsson, 1988).
Procedure
After the SEMG sensors were positioned and before the start of the wear trial, several MVC trials were performed on the right hand for normalization purposes. The time taken at wear trial for each of the hand conditions was around 30 min; the schedule is illustrated in Figure 2. At the beginning of the wear trial, the participants were asked to put on one of the gloves and rate their perception of the glove by using the subjective scales. Then they had to grip a dynamometer, move 30 marbles, button a shirt, and type an essay for 15 min. The four tasks were designed to represent the routine hand tasks and difficulties during daily living activities as reported by burn rehabilitation patients. Two minutes of rest were allowed between each activity. At the end of the tasks, the participants were asked to complete the subjective scales again. The wear trial had to be carried out four times by each participant to test the four hand conditions in randomized order. All of the wear trials carried out by the same participant were completed on the same day, and there was at least 30 min of rest between each wear trial. A demonstration of the wear trial procedures was given to the participants. Prior to the start of the wear trials, the participants were allowed to practice and become accustomed to the assigned four tasks so as to achieve a regular pace and rhythm during the given tasks. During the wear trial of the pressure glove, the participants were also given a short practice before the start of each task.
Wear trial process.
Gripping task
The grip strength of the hand was measured with a Jamar hand dynamometer, which has been reported as a highly reliable and valid tool (Härkönen, Harju, & Alaranta, 1993; Mathiowetz, 2002; Mathiowetz, Weber, Volland, & Kashman, 1984; Shechtman, Gestewitz, & Kimble, 2005). The dynamometer was set to the second handle position (4.8-cm grip span) for all of the testing and placed onto a table. The participant was asked to hold the dynamometer with a straight wrist and elbow angle of about 90°. The participant had to exert maximal gripping effort onto the dynamometer for 5 s within which the 1-s averaging window with the highest SEMG amplitude was extracted for EMG data. The gripping task was performed once for each condition.
Moving marbles
The test that involved the moving of marbles was designed to examine the ability of the hand to hold and handle a smooth, round object. The marbles were 2 cm in diameter. Two boxes, which were 31 cm apart from each other, were placed in front of the participant. There were 30 marbles inside the box on the right. The participant was asked to transport all 30 marbles, one at a time, to the box on the left by only using his or her right hand. The participants were allowed to complete the task at their own pace and comfort and were asked to keep this pace throughout the entire wear trial. The SEMG data of the first and last 3 s were excluded from the data analysis.
Buttoning a shirt
The participants were requested to button all of the buttons on the front placket of a dress shirt, which was laid flat on a table. The shirt used was a regular female dress shirt in U.S. size 4 with seven buttons (10 mm in diameter) on the front placket. Similar to the marble-moving task, the participants were allowed to complete the task at their own pace and comfort and were asked to keep this pace throughout the entire wear trial. The SEMG data of the first and last 3 s were excluded from the data analysis.
Typing
A notebook computer (Precision M4700, Dell, USA) was prepared for the participants to type a standard essay for 15 min. The essay was presented as a soft copy in Microsoft Word and shown on the left side of the computer screen. Another blank Microsoft Word window was opened on the right side of the screen for the participants to type the essay. The participants were requested to complete the task at their normal typing speed and to keep their pace constant throughout the typing task. They were allowed to correct typing errors as in usual practice. The SEMG data were extracted from three time frames, which were at 1 to 1.5 min (Period 1), 7 to 7.5 min (Period 2), and 14 to 14.5 min (Period 3).
Psychophysical assessment
In the psychophysical assessment, participants were asked to rate the wearing comfort and ease of hand motion of each glove condition by using a 9-point rating scale (Figure 3). A Borg 6-to-20 Rating of Perceived Exertion Scale was also adopted to quantify the exertion of hand when gloves were worn during the hand motions (Borg, 1982; Purvis & Tunstall, 2004). The rating of each scale was reported right after the glove was put on and after the completion of all the tasks.
Rating scales for psychophysical response.
Statistical Analysis
The data obtained from the experiment were analysed with SPSS 19 (IBM Corp., Armonk, NY, USA) statistical software. Repeated-measures ANOVA was adopted to analyze the effect of the four hand conditions on (a) %MVE at P10, P50, and P90 of APDF of the three muscles in completing the various tasks of the wear trial, (b) time consumed in moving the marbles and buttoning the shirt, (c) number of words typed in typing task, (d) gripping strength, and (e) results of the psychophysical assessment. Post hoc Bonferroni pairwise comparison was used to further evaluate the impacts caused by the different hand conditions. Paired-sample t testing was used to compare the results of the psychophysical assessment at the beginning and end of the wear trial. Spearman’s rank coefficient was adopted to evaluate the correlation between psychophysical perception and the RF of a glove. The alpha level was set at 0.05 for statistical significance.
Results
Muscle Activities
The %MVE of the three muscles at P10, P50, and P90 of APDF during the different tasks of the wear trial and the results of repeated-measures ANOVA among the four hand conditions are presented in Figure 4 and Table 2, respectively. The average time taken to complete the task of moving the marbles and buttoning the shirt were 34.57 ± 4.69 s and 32.92 ± 6.05 s, respectively, and there were no significant differences between the four hand conditions of the wear trial. The average number of words completed in the typing task was 502.95 ± 78.23 words. Although significant difference was found between the bare-hand condition and the gloved conditions, the pairwise comparison showed no significant difference among the three gloved conditions.
Muscle activities (percentage maximum voluntary electrical activation) at static level (P10), median level (P50), and peak level (P90) of the amplitude probability distribution function of flexor pollicis longus, extensor digitorum, and flexors digitorum superficialis during (a) moving marbles, (b) button a shirt, and typing at (c) Period 1, (d) Period 2 and (e) Period 3 under different hand conditions.
Repeated-Measures ANOVA Results of the Effect of Hand Conditions on the Static Level (P10), Median Level (P50), and Peak Level (P90) of the Amplitude Probability Distribution Function of the Three Muscles During Different Tasks
Note. FPL = flexor pollicis longus; ED = extensor digitorum; FDS = flexors digitorum superficialis;
p values < .05 are bolded.
In the task that involved buttoning a shirt, significant differences were found for the APDF P10 of FPL and ED and for the APDF P50 and P90 of all the three muscles among the four conditions. For each muscle, the APDF (except FPL P90) of the bare-hand condition was at the highest level among the four hand conditions and that of FDS decreased as the RF increased. When compared with the bare-hand condition, the APDF P10, P50, and P90 of the FDS when wearing the glove with RF of 20% were reduced by 0.8%MVE, 2.76%MVE, and 8.78%MVE, respectively. From the results of pairwise comparison, the FPL showed significant differences in the pairing of the bare-hand condition with the glove that had an RF of 15% for APDF P10, P50, and P90 and in the pairing of the glove with an RF of 10% and that with an RF of 15% for APDF P90. For the ED, significant difference was also found between the pairing of the gloves with RFs of 10% and 15% for APDF P50. In addition, a pairwise comparison of each condition with the bare-hand condition showed significant differences at various level of APDF. Significant differences were found for the APDF P90 of the FDS in the pairwise comparisons between the bare-hand condition and the glove with an RF of 15% and between the bare-hand condition and the glove with an RF of 20%.
The APDF of the three muscles showed a similar trend among the three time frames of the typing task. During Period 3, the APDF P10 and P50 of the ED and the APDF P50 and P90 of FDS had significant differences among the four hand conditions. Even though the APDF of these two muscles showed an increase in %MVE with the RF, only the difference between the bare-hand condition and a glove with an RF of 20% was found to be significant in the pairwise comparisons. No significant difference was found in the APDF P10, P50, and P90 of the three muscles during the moving-marbles task and in Periods 1 and 2 of the typing task.
Maximum Power Grip Force
The maximum grip force under different hand conditions and the corresponding APDF P90 are presented in Figure 5. The hand condition has no significant effect on the muscle activities of the three muscles. The participants showed a high level of compliance to the experiment and provided maximum grips under all hand conditions using a similar muscle activities level, which agrees with the finding by Kovacs et al. (2002). However, an overall significant difference was found for the maximum grip force between the bare-hand and three gloved conditions (p = .03). The maximum grip force across all of the participants was 37.2 ± 8.6 kg in the bare-hand condition, whereas it decreased by 3.4 to 4.4 kg in the gloved conditions. The hand conditions affect the force output during the action of gripping. However, no significant difference was found in the pairwise comparison, which indicates the RF of pressure glove did not contribute to the force output at gripping.
Grip force and amplitude probability distribution function peak level of flexor pollicis longus, extensor digitorum, and flexors digitorum superficialis during gripping under different hand conditions. Error bar represents the standard error.
Psychophysical Assessment
The psychophysical ratings were conducted at the beginning and at the end of the wear trials to measure the subjective perceptions of the applied pressure when gloves are worn and the possible change of perceptions after the four tasks. No significant difference was found between the psychophysical assessment at the beginning and end of the wear trial except for the rating on the motion perception of the glove with an RF of 10%. The results of the Spearman’s rank correlation (Table 3) showed that the RF of the glove is significantly correlated to the psychophysical perception. The perceived comfort, hand motion and exertion, and the perceptions at the beginning and end of the wear trial are also correlated to each other. The results obtained at the end of the wear trial are shown in Figure 6. The increase of glove tightness (from an RF of 10% to 20%) adversely affects the perceived exertion, glove comfort, and ease of motion. The results of the repeated-measures ANOVA among the four hand conditions showed a significant difference for all of the perceptions. The corresponding pairwise comparisons showed that significant differences are evident in a comparison between the gloves with an RF of 10% and an RF of 20% in terms of all three different types of perceptions and between the gloves with an RF of 15% and 20% in terms of the perceived ease of motion.
Spearman’s Rank Correlation (rs) Among Perceived Comfort, Hand Motion and Exertion, and the Reduction Factor (RF) of Glove
Note. All correlations are significant at p < .05.
Psychophysical assessment at the end of wear trial. Significant differences between glove tightness are noted by a common superscript. Error bar represents the standard error.
Discussion
This SEMG-based study illustrates the response of the forearm muscles to different types of activity when the hand and finger motions are restricted by a pressure therapy glove. Significant differences in the APDF P10, P50, and P90 of FPL, ED, and FDS among the different hand conditions can be found only in the buttoning-of-a-shirt and typing tasks, not in the moving-marbles task. The moving-marbles activity required the participants to grasp, hold, and release 30 marbles by using their fingers and moving their forearms to carry the marbles. Grasping, holding, and transporting a small object are routine hand tasks in daily life. From the results of the moving-marbles task, it is observed that the presence of a pressure glove and its tightness do not significantly affect the pattern of activity of the muscles that were monitored in this study.
For buttoning a shirt, the muscle effort is required not only to hold the buttons but also to pass them through the small buttonholes, resulting in higher overall forearm muscle activity than moving marbles. The hand dexterity and the range of finger motion required become more demanding in handling smaller objects. With the pressure glove, the muscle activity of the FPL, ED, and FDS during the buttoning of the shirt decreased in comparison to the bare-handed condition. In the current study, the presence of glove and its tightness could have led to a change in muscle utilization patterns during fine and dexterity-demanding hand activities, such as buttoning a shirt.
Changes of arm muscular activities in the gloved conditions can also be found during Period 3 of the typing task. As the participants may need an acclimation period to become accustomed to the typing motion when the pressure glove is worn, there is no significant difference in muscle activities among the hand conditions in Periods 1 and 2. The level of APDF is relatively low during typing (with APDF P50 of FPL <3.57%MVE) as compared with other assigned tasks, such as buttoning a shirt (with APDF P50 of FPL >7.7%MVE) and moving marbles (with APDF P50 of FPL >5.88%MVE). The anticipated finger force at typing and pressing the keyboard is relatively small. As shown in Figures 4 and 5, the muscle activity requirements in typing are not as high as the tasks that involve grip action. However, the typing action involved a higher frequency of finger, hand, and wrist combination movement (Pereira et al., 2013). An increase in level of forearm muscle activity with a glove of higher RF showed that more muscle effort is given by the participants to complete the typing task. Additional muscle effort may be spent to work against the pressure delivered from the tighter glove. The presence of a pressure glove with a high RF of 20% adopted could bring about an increase in the muscle demand for typing actions, which involve high-frequency but low-force-intensity motions. The adjustment of muscle utilization in completing the buttoning task or the increase in muscle demand at typing induced by the pressure therapy glove could be one of the factors leading to a negative perception of comfort, ease of motion, and exertion.
In the case of the gripping task, the participants had a similar muscle activity but with difference in force output under different hand conditions. Muscle activation is not the major factor that drives a reduced maximum grip force. As indicated by Dianat, Haslegrave, and Stedmon (2012a), the effect on handgrip strength could be due to the reduction in friction at the glove–object or hand–glove interface and hence could increase the likelihood of slippage. The friction and the tightness of the gloves may be the contributing factors for the change in force output between the bare-hand and gloved conditions. As some of the force was used against the pressure delivered by the pressure glove, the grip strength recorded showed a significant decrease. On the other hand, the grip strength difference was not significant in the pairwise comparisons between the wearing of gloves with different RFs. The difference in pressure delivered to the hand among the different RFs was not large enough to make a difference to the maximum grip strength measured. This finding means that with the use of a pressure glove, the maximum grip strength can be affected, but the impact caused by an RF between 10% and 20% is not obvious. Hence, to preserve the maximum grip strength, clinicians should focus on not only the amount of RF and the tightness of the glove but also the choice of glove fabrication, such as fabric surface properties.
The psychophysical sensation of the pressure glove is closely associated with the acceptance and compliance of the pressure treatment. The increased glove pressure with applied RFs of 10%, 15%, and 20% lead to a consistent increase in the perceived exertion level of hand motion. Participants’ perceived comfort and ease of motion also gradually decreased with increased RFs of the glove. The perceptions have a significant difference when the glove tightness changed from 10% to 20%. Apart from the reduction in handgrip strength and the change in muscle activities of forearm, the increased glove tightness also contributes to a decrease in perception of comfort and ease of motion.
A limitation of the study is that the wear trial was only 30 min. The participants were first fitted with the pressure therapy glove. They were allowed to freely move their hands to obtain the feelings of wearing the glove and to practice for a few seconds before the start of each task. The period of time allowed for adjustment to the glove might not have been enough. The impact of the glove after it was worn for a period of time and the impact on muscle fatigue are not evaluated. A longer investigation on the muscle activity is recommended so as to understand the change in muscle activity after the participant becomes accustomed to the glove and the muscle fatigue. Apart from this limitation, a regular fitted pressure glove with no RF was not included in the experiment. The wearing of a no-RF glove could impact the dependent variables in the study. Therefore, a glove with no RF was not considered in this study.
Another limitation is that only participants without hypertrophic scars are included in the study. The presence of hypertrophic scars on the hands could restrict and alter the hand motions in handling different activities. Apart from the psychophysical sensation, the pain caused by the scars can be another important concern in the treatment of burn rehabilitation. The impact of the pressure glove on hands with these scars is essential for reflecting real-life scenarios. However, the uniqueness of the scars at the same time affects the level of muscle activity in different ways and the impact of the pressure glove. The present findings can verify the impact of the pressure gloves on normal hands. The extending of the study to include hypertrophic scars patients is recommended so as to investigate the combined effect of pressure glove and hypertrophic scars on muscle activity.
Conclusions
Pressure glove tightness induced by the reduction in circumferential dimensions negatively affects the psychophysical sensation and handgrip force. Gloves with tighter pressure contribute to lower perceived comfort and ease of hand motion, which may adversely influence the rate of patient compliance during the course of treatment. When a pressure glove is worn, the muscle activity is affected in different ways throughout the performing of different tasks. When pressure gloves with an RF of 15% and 20% are worn, the muscle activity of the ED and FDS shows a significant decrease in comparison with buttoning a shirt with bare hands. Future research that included sampling of additional muscles would be required to explain which muscles are in use and to what extent. In terms of typing, the muscle activity of these two said muscles is increased with a pressure glove that has an RF of 20%. To improve adherence to pressure gloves, comfort and muscle strength in performing daily activities should be taken into consideration in their prescription.
Key Points
When a pressure glove is worn, it results in a reduced maximum gripping force.
Gloves with tighter pressure contribute to lower perceived comfort and ease of hand motion.
Pressure gloves with a high reduction factor (RF) of 20% increase the muscle activity of the extensor digitorum (ED) and flexor digitorum superficialis (FDS) compared with the bare-hand condition while typing on a keyboard.
Among the three forearm muscles studied, the increase in RF to 15% and 20% for pressure gloves was associated with reduced muscle activity of the ED and FDS during the buttoning task.
No significant influence on the forearm muscles that control finger motions was found for the moving-marbles activity.
Footnotes
Acknowledgements
We would like to thank the Research Grant Council (PolyU 5329/10E) and the Departmental Grant of the Institute of Textiles and Clothing, Hong Kong Polytechnic University (PolyU RPXS), for funding this research project.
Annie Yu is a PhD candidate in the Institute of Textiles and Clothing of the Hong Kong Polytechnic University. She received her BA (Hons) degree in textile technology from the Hong Kong Polytechnic University in 2010.
Kit Lun Yick is an associate professor in the Institute of Textiles and Clothing of the Hong Kong Polytechnic University. She specializes in fashion production technology and product development. She has carried out scientific studies in the areas of anthropometry measurements, comfort evaluation, and fabric thermal properties for patients in hospitals.
Sun Pui Ng is a lecturer in Hong Kong Community College of the Hong Kong Polytechnic University. He received his BEng (Hons) and PhD degrees from the Department of Mechanical Engineering of the Hong Kong Polytechnic University in 1994 and 2001, respectively. He has taken part in projects to integrate mechanical engineering principles with textiles technologies, and his expertise lies in new development of engineering materials and functional textiles.
Joanne Yip is an assistant professor in the Institute of Textiles and Clothing of the Hong Kong Polytechnic University. Her research interests include new materials (spacer fabric, EAP, IPMC) and technology (liquefaction, electrospinning), surface treatments on textiles (plasma and laser treatment), and moulding or seamless techniques used in intimate apparel.